In use of catheters for introduction into a body cavity, a process called catheterization, it is common in some instances to include on the catheter itself an inflatable balloon or "cuff" which is inflated after introduction of the catheter to prevent accidental retraction or rejection of the catheter. It is usual to inflate the cuff from an outside source of air as, for example, a bulb pump. Representative of the prior art in this field is a Weikl et al, U.S. Pat. No. 4,573,966.
The present invention is directed to a self-inflating cuff which can be used when the catheter is utilized for perfusion of liquid into a body cavity. One known means of accomplishing this inflation is to provide the catheter with an inflatable cuff surrounding the outside of the catheter spaced from the distal end. Openings into the cuff from the catheter lumen are provided spaced axially of the lumen, and the sides of the distal end of the catheter are provided with a plurality of small openings for outflow of the perfusion liquid. The end of the lumen, in this known device, is closed off and the openings are designed such that the pressure in the lumen will exceed the pressure in the vessel and will, as a result, exert pressure on the interior of the cuff to cause inflation. Thus, pressure flow divides with a portion entering the cuff and a second larger portion exiting the catheter lumen. The fluid portion entering the cuff remains in the cuff as long as fluid is flowing through the lumen and therefore becomes stagnant. This is an undesirable condition particularly when blood or blood elements comprise part of the solution delivered through the catheter. See U.S. Pat. No. 5,021,045 (Jun. 4, 1991).
The cannulae may be placed in small friable vessels in the body. One known instance would be placement in the coronary sinus of the heart. Existing catheters monitor the pressure of the coronary sinus either at the end of the catheter or along the outside of the distal portion of the catheter. When the vessel size is close to the diameter of the catheter, the force of the pressure exiting the catheter through radially oriented holes can force the catheter against the wall of the vessel and thus cause the pressure monitoring port to become occluded. Similarly, a sharp turn in the vessel can cause the monitoring port at the tip or side to occlude. When the monitoring port is thus occluded, excessive pressure can be generated in the central lumen of the catheter and subsequently in the balloon, since flow through the cannulae is stopped or reduced. This excess pressure has been known to rupture the coronary sinus.
Similarly, catheters with multiple holes in the cuff area have a tendency to buckle in this area. A common means of preventing bucking in the catheter body is to include a reinforcing wire spring into the wall of the catheter. However, it is difficult to continue this spring into the cuff area since punching the holes will expose many sharp ends that could damage the cuff.
The present invention provides an improved self-inflating cuff which reduces stagnation of inflating media in the cuff. All of the fluid passing through the catheter exits the lumen at the cuff, passes through the chamber formed between the cuff and the outside of the catheter, and returns to the catheter lumen for subsequent delivery to the body cavity. A further object is to provide a reinforcement to prevent unintentional collapse of the catheter in the cuff area. Pressure monitoring is important in the use of a perfusion function and an object is also to allow monitoring of the cuff pressure and central lumen pressure as well as the approximation of vessel pressure depending upon the flow through the catheter.
Pressure that approximates the intra-vessel condition in normal operation will be sensed through the pressure lumen and its associated openings. However, should the lumen of the catheter become blocked simultaneously with the outlet of the pressure monitoring lumen, the opening between the pressure lumen and the catheter lumen will indicate undue pressure in the cuff which requires immediate attention of the monitoring personnel. Other objects include a lumen plug which serves the dual purpose of assisting in the introducing of the distal end of the catheter into a vessel, and diverting flow from the lumen through the balloon and subsequently into the distal portion of the lumen beyond the plug.
Other features of the invention will be apparent in the following description and claims in which the invention is described together with details to enable persons skilled in the art to practice the invention, all in connection with the best mode presently contemplated for the invention.